A wide variety of wireless communication techniques have been developed to facilitate wireless telecommunication. In this disclosure, the phrase frequency division multiple access (FDMA) broadly refers to any wireless communication technique in which an allocated frequency spectrum is divided into a plurality of smaller frequency cells. Each cell of the allocated spectrum has a carrier signal that can be modulated with data. Dividing the allocated frequency spectrum into cells can increase the amount of data that can be communicated over the spectrum, and also provides an easy mechanism for apportioning bandwidth to service providers. For example, specific cells may be assigned to specific service providers, and the wireless network of a given service provider may use one or more cells in order to provide service to its subscribers.
In this disclosure, the phrase time division multiple access (TDMA) broadly refers to a wireless communication technique in which frequency cells are divided into time slots. In systems that implement TDMA techniques, different wireless communications are sent during specific time slots, and in some cases, time slots can be allocated for reservation-based communication. In this way, a single frequency cell can support multiple time-divided communication channels.
The global system for mobile communications (GSM) standard, standardized by the European Telecommunication Standards Institute (ETSI), is one example of a system that makes use of FDMA and TDMA techniques. In Europe, for example, frequency bands surrounding 900 megahertz (MHz) and 1800 MHz have been allocated for GSM. The frequency bands surrounding 900 and 1800 MHz are divided by GSM into approximately 548 frequency cells of approximately 200 kilohertz (KHz) per cell. Within each cell, TDMA techniques are implemented, in which time slots are used for time-allocated communication. The different cells can be assigned to different service providers for use in the service providers networks. Some cells are used as network beacons to inform subscriber units which cells are associated with a given network, while other cells are used only for delivering network traffic to and from subscriber units.
One challenge in systems that implement FDMA techniques, such as GSM, is the process of cell selection or acquisition by a subscriber unit. A subscriber unit refers to a device such as a mobile radiotelephone, or the like, which is used by the end user. In an FDMA system, the subscriber unit scans the various cells of the allocated spectrum and measures the power of the cells, looking for the most desirable cell for telecommunication. The most desirable cell is typically a cell associated with the network of the service provider of the subscriber unit, or possibly a cell for which the service provider of the subscriber unit has a favorable roaming agreement. Cells having higher power signals are also more desirable to a given subscriber unit than lower power cells, e.g., when choosing between cells in the network of a given service provider.